The present invention relates to a refrigeration apparatus for use in an air conditioner and, more particularly, to a refrigeration apparatus having a gas injection line.
Generally, a refrigeration apparatus having a gas injection line includes a refrigerant circuit which is constituted by a compressor, condenser, first pressure reducer, gas-liquid separator, second pressure reducer and an evaporator which are connected in series to form a closed circuit for refrigerant. The gas injection line has a pipe which is connected at its one end to the gaseous phase portion of the gas-liquid separator while the other end is connected to the cylinder chamber (compression chamber) of the compressor under compression stroke.
The gaseous refrigerant of high pressure discharged from the compressor is introduced into the condenser and is liquefied in the condenser to become liquid refrigerant through heat exchange with a fluid such as air or water which also is made to flow through the condenser. The liquid refrigerant from the condenser is decompressed to an intermediate pressure as it flows through the first pressure reducer so that a part of the refrigerant is evaporated into gaseous phase. The gaseous and liquid phases of the refrigerant are introduced into the gas-liquid separator and are separated from each other. The liquid phase of the refrigerant is discharged from the liquid phase portion of the separator, and is introduced into the evaporator after a decompression to a predetermined low pressure through the second pressure reducer. In the evaporator, the liquid refrigerant is evaporated as it absorbs heat from the fluid such as air or water which also is made to flow through the evaporator. The evaporated refrigerant is then returned to the compressor. On the other hand, the gaseous phase of the refrigerant, which has been separated from the liquid phase and accumulated in the upper part of the gas-liquid separator, is injected into the compression chamber of the compressor under compression stroke through the gas injection line thereby increasing the heating or cooling power of the air conditioner incorporating the refrigeration apparatus.
Japanese Utility Model Laid-Open No. 22657/1983 discloses a refrigerant circuit having a gas injection line of the type mentioned as above. This refrigerant circuit suffers a problem that, when the load is changed to reduce the difference of pressur between the high-pressure side and the low-pressure side, the liquid level in the gas-liquid separator is raised to undesirably allow the liquid refrigerant to come into the gas injection line, partly because the dryness of the refrigerant coming into the gas-liquid separator is reduced and partly because the flow rate of the refrigerant through the second pressure reducer is decreased. Consequently, the liquid refrigerant is injected into the compressor to cause problems such as an increased power demand by the compressor and, in the worst case, a breakdown of the compressor. The reduced flow rate of the refrigerant through the second pressure reducer undesirably increases the degree of superheating of the refrigerant gas at the evaporator outlet, resulting in a reduction of the cooling or heating power.
In some air conditioners, an outdoor unit having the compressor, condenser, first pressure-reducer and the gas-liquid separator is installed on a lower floor of a house, while an indoor unit having the second pressure reducer, evaporator and so forth are installed on an upper floor so that both units are connected through pipes of considerably large lengths. In such a case, the refrigerant pressure at the inlet to the second pressure reducer is lowered due to a pressure drop along the long pipes so that the flow rate of the refrigerant is decreased undesirably. Since the liquid refrigerant in the gas-liquid separator is saturated, bubbles of refrigerant gas are mingled in the liquid refrigerant separated by the gas-liquid separator as a result of the pressure drop mentioned above, and this pressure drop is further increased by the bubbles of the refrigerant gas. This also increases the tendency of the rise of the liquid level in the gas-liquid separator to undesirably permit the liquid refrigerant to be injected into the compressor through the gas injection line. At the same time, the flow rate of the refrigerant through the evaporator is decreased to reduce the cooling power of the refrigeration cycle.